There are times when an exact answer is needed and times when it is not. Approximation further develops an understanding of what is reasonable within a given context.
“Mental math enables students to determine answers and propose strategies without paper and pencil. It improves computational fluency and problem solving by developing efficiency, accuracy, and flexibility.”1
1Ministry of Education, S. (2020). Retrieved 20 June 2020, from https://curriculum.gov.sk.ca/bbcswebdav/library/curricula/English/Mathematics/Mathematics_7_2007.pdf